What brand CPAP? Check with the manufacturer for the 12V requirements and then meter the outlet with the other demands coming on and off and watch what's happening.
Both my Respironics Tranquility Plus and the Puritan Bennett GoodKnight 420 runs on 110v and extension cord without complaint using a cheapo inverter - I have not yet wired a 12v outlet close enough to the bed to warrant chasing down a 12v cord for the PB.
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I use a marine deep cycle battery in the car for everything.
There is a 750 watt Power Inverter in the trunk of the car connected with a #8 guage wire to the battery under the hood.
It runs my C-Pap all night and a reading lamp (low energy) 16 watt prior to going to sleep. I shut the KOOLATRON Kargo Cooler-p65 off prior to lights out.
A larger Inverter is a better way to go. It will operate a 1/2 "drill, coffee maker, reciprocating saw ect. I paid $42,97 for the unit. The higher wattage is a little more noisy compared to a smaller version, is the reason it was located in the trunk.
Thanks for all the responses. These forums are so cool.
Well, I was just outside in the TT, playing around with a voltmeter. Indeed, a few of you nailed at least one part of the problem - I'm losing way too much voltage in the wires, looks like a drop of just over .5 volts, from battery terminals to the actualy outlet the CPAP plugs into.
I also bought a cheap (probably too cheap, LOL) 100 watt pocket inverter from Walmart today and tried it. Did not help any, and actually seemed to make it worse. Of course, I plugged the inverter in the same (bad) 12V outlet where the CPAP was plugged into, so the same voltage drop issue was there, as well as the fact it was probably just not a very good inverter. Oh, well, that inverter will be going back to Walmart soon (they take back anything, so figured I had nothin to lose trying).
Soooo, I think no matter what the solution is, next thing I need to do is run a new 12V wire directly from the battery to the 12V outlet for the CPAP machine. Fortunately, I have a ton of left over very heavy gauge wire, from when I upgraded the main wires going from the battery to the converter. Will be overkill, but I think I'll use it. Once I have the re-wirin done, we'll see if the CPAP will work OK directly off of 12V, or if I need to think about an inverter or separate battery at that point.
Oh, I looked at that CPAP.com web page a previous poster pointed out. Nice battery packs they have there, but awful pricey! Sheez, I could put in a new pair of Trojan T105s solely for the CPAP to use, for a lot less than what many of those listed at CPAP.com cost!!
Will & Angela
2 wonderful children that love camping, Stephen & Allison
2003 Ford Excursion V10 4x4
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Quote: A larger Inverter is a better way to go. It will operate a 1/2 "drill, coffee maker, reciprocating saw ect. I paid $42,97 for the unit. The higher wattage is a little more noisy compared to a smaller version, is the reason it was located in the trunk.
I must admit I don't know much at all about inverters, never had the need for one before. Except for the ability to run other, more power-hungry appliances (which I don't see us ever needing to do), is there other advantages to a larger, more expensive inverter? Would larger ones hold a good output AC current better when the input voltage drops some?
Based on the noise I'm reading that the cooling fans in many inverters make, I'm beginning to not like the inverter idea. Seems like that cooling fan would rob some power, making the situation worse for what I want to do. That is, unless it really will help keep power output consistent to the CPAP when the battery voltage drops a little due to other loads.
Will, go with the oversize wire first and see if that works. The inverter will hold the voltage constant but as you suspect there will be a power penalty. Even if you do use an inverter you will want the 12 volt wire upgraded anyway.
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a larger inverter will deal with the voltage drop better, also i bought a charger/inverter that plugs in and is automatic switching, it uses very little power on standby
I would check voltage going into the machine first. Could be bad wiring or just your connecter cord. Those cig lighter connections are trouble-prone. My Remstar has worked for years on DC.
Bill and Susan
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